Scaling the Feeding Mechanism of Captive Alligator mississippiensis from Hatchling to Juvenile.

James Kerfoot,Ruth Elsey,Micah Fern

doi:10.3390/biology3040724

Abstract

Small changes in size can lead to potential performance consequences and may influence an organism’s ability to utilize resources in its environment. As the American alligator (Alligator mississippiensis) transitions between neonate, juvenile and adult habitats (ontogenetic niche shifts), there are inevitably dynamic changes in their feeding performance. This study sought to investigate the scaling of the feeding mechanism and its performance from hatchling to juvenile size classes in A. mississippiensis. Feeding events were recorded during March 2011 at Rockefeller Wildlife Refuge (Grand Chenier, Louisiana). Thirty-six captive individuals were randomly sampled, ranging from 30.5 cm to 91.5 cm total length, and feeding events were recorded using a high speed camera at a rate of 300 fps. Results indicated that many linear, angular and timing kinematic variables scale allometrically with cranium length; whereas maximum gape velocity and duration of feeding bout do not scale with cranium length and remain constant between these size classes. Although it has been shown that there is an isometric relationship between cranial elements and body size in A. mississippiensis, this relationship is not transferred to linear and timing variables of prey-capture events. These allometric relationships echo other investigations of scaling relationships such as bite-force production and terrestrial locomotion.

Highlights

Small changes in morphology or simple changes in size can lead to novel functions and the potential for performance consequences [1]
Even though this study indicated that the log-transformed skeletal jaw elements scaled isometrically with log-transformed body size (Figure 4, Table 3), both maximum gape and cranial rotation had slight positive trends, and were significantly different from the predictions of the geometric similarity model (GSM)
It has been shown that there is an isometric relationship between cranial elements and body size in juvenile A. mississippiensis, these isometric relationships are not transferred to linear and timing variables of prey-capture events in these two size classes studied

Summary

Introduction

Small changes in morphology or simple changes in size can lead to novel functions and the potential for performance consequences [1]. An organism’s ability to utilize its environment is often determined by body size and its influence on performance [2]. Weighing approximately 65 g at birth and eventually growing 4000-fold by adulthood, Alligator mississippiensis (Daudin 1801) provides a model to investigate the influence of body size on performance [3,4]. Throughout ontogeny limbs become relatively shorter, with distal limb segments becoming increasingly shorter relative to proximal segments [3,7,8]. This negative allometry of distal limb lengths and proportions causes A. mississippiensis to become more dependent on aquatic environments as growth increases [3]

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